This invention relates to surgical instruments, and in particular to powered arthroscopic surgical instruments.
Arthroscopic surgical instruments typically include an rigid outer tube within which a rigid inner tube is rotated by a motor. A cutting implement, such as a blade or abrading burr, is disposed on the distal end of the inner tube. Tissue or bone is exposed to the cutting implement through an opening in the distal end of the outer tube, and tissue or bone fragments cut by the rotating blade or burr are drawn through the interior of the inner tube along with irrigating fluid by the use of suction applied at the proximal end of the instrument. Examples of such surgical instruments are described in U.S. Pat. Nos. 4,203,444, 4,274,414, 4,834,729, and 4,842,578, all of which are assigned to the present assignee.
In some instruments, the cutting implement is a hinged jaw mounted on the outer tube near its distal end, and is actuated by the rotating inner tube to pivot on the hinges and cut tissue. Examples of these surgical instruments are described in U.S. Pat. Nos. 4,522,206, 4,662,371, both of which are assigned to the present assignee.
Typical arthroscopic surgical instruments are linear, that is, straight between their proximal and distal ends. It is sometimes useful for such instruments to be curved to facilitate positioning the cutting implement against tissue to be cut without requiring that the instrument be removed from the body and reinserted through an additional puncture. A region of the inner tube is flexible to enable the inner tube to accept the curvature imposed by the outer tube while transmitting the torsion applied by the motor to the blade.
In Trott, U.S. Pat. No. 4,646,738, the inner tube is made flexible with a separate flexible section made from a series of coaxial, spiral layers wound in opposition. The cutting blade is welded to the distal end of the counter-wound helical coils, and the rigid proximal end of the inner tube is secured to the other end of the flexible structure. During operation, torque generated by rotation of the motor in one direction is transmitted to the blade by the tightening of the coil or coils that are wound in that direction, which also serves to counteract the tendency of the oppositely wound coils to be unwound by the rotation.